1. Field of the Invention
The present invention relates to an irradiation device that is suitably used for characteristic evaluation, light resistance test (e.g., fading test or the like) or the like for a device such as a solar cell or the like.
2. Background of the Related Art
An artificial (pseudo) sunlight irradiation device for emitting light having substantially the same spectral characteristic as sunlight (hereinafter referred to as “artificial sunlight”) has been hitherto known, and broadly used for characteristic evaluation, light resistance tests (fading tests), etc. for solar cells (see JP-A-2009-2649912 and JP-A-2009-218009, for example).
The applicant (inventor) has filed an international application (PCT/JP2011/066531) for an artificial sunlight irradiation device in which a spectrum correction filter for converting the spectral characteristic of a light source to the spectral characteristic of sunlight and a light attenuating filter such as a neutral density filter (ND filter) for adjusting the amount of light are freely exchangeably provided on an optical path extending from the light source to an irradiation face so that the spectral characteristic of the artificial sunlight and the light amount thereof can be easily adjusted.
When the spectrum correction filter and the neutral density filter are provided on the optical path, reflection light reflected from a film face coated on one of the filters is reflected from a film face on the other filter and mixed with irradiation light to the irradiation face. When this reflection light is based on reflection from the film face of the spectrum correction filter, the spectral characteristic is modulated due to the reflection at the spectrum correction filter. Accordingly, when the reflection light as described above is mixed with the irradiation light, the spectral characteristic of the irradiation light is deviated from a desired design value. Therefore, there is a problem that it is impossible to obtain irradiation light whose quality is matched with characteristic evaluation and the purpose of light resistance tests.